Synthesis of polycarbonate from dimethyl carbonate and bisphenol-a through a non-phosgene process

A novel nonphosgene process for producing bisphenol-A polycarbonate (PC) was developed through a transesterification between bisphenol-A (BPA) and dimethyl carbonate (DMC) and a melt-polycondensation of the resulting bisphenol-A bismethylcarbonate (1). The transesterification was carried out by heating bisphenol A in dimethylcarbonate in the presence of Lewis acid catalysts, removing the by-producing methanol using molecular shieves 4A. Among various catalysts, a combination of (Bu2SnCl)2O and dimethylaminopyridine gave the best results to produce 1 in 22% yield for 48 h. Using a larger amount of the molecular sieves further improved the yield to 80% in 120 h. The resulting 1 was heated under reduced pressure in the presence of titanium catalysts to produce PC in good yields. The resulting PC had high weight average molecular weight (Mw) of 75,000.